Gas blast circuit breaker using a generally axial flow main blast

ABSTRACT

Discloses a gas-blast circuit breaker comprising an upstream electrode, a downstream electrode spaced therefrom, and an orifice having an opening positioned between said electrodes. During interruption, an arc established between the electrodes extends through the orifice opening, and a gas blast is caused to flow through the orifice opening via paths extending along the external surface of the upstream electrode and generally axially of the arc adjacent the upstream electrode. Improved flow conditions adjacent the upstream electrode are produced by providing a series of jets issuing from circumferentially-spaced points about the orifice opening and directed convergently toward the central region of the downstream face of the upstream electrode.

United States Patent [72] Inventor John W. Beatty 3,270,173 8/1966Barkan.... ZOO/148(2) Newtown Square, Pa. 3,288,969. 11/1966 Reece200/148 [2]] Appl. No. 761,674 3,435,166 3/1969 Barkan ..200/ 144(APRT){22] Filed Sept. 23 1968 4s Patented Mayl8, l97l Pmm'y [73] Assi eeGeneral Electric Com an Att0meysJ. Wesley Haubner, William Freedman,Melvm M.

p y Goldenberg, Frank L. Neuhauser and Oscar B. Waddell [54] GAS BLASTCIRCUIT BREAKER USING A M E RALL AXIAL MAIN G NF Y -FLow BLAST ABSTRACT:Discloses a gas-blast circuit breaker comprising 5 Claims, 3 DrawingFigs.

an upstream electrode, a downstream electrode spaced [52] US. Cl th fand an orifice having an opening positioned between said electrodes.During interruption, an are [5 l Int. Cl 01h 33/70 established betweenthe electrodes extends through the ifi ofsml'ch opening and a gas iscaused to flow through the orifice I482, 144 opening via paths extendingalong the external surface of the upstream electrodevand generallyaxially of the arc adjacent [56] g s gl gs gglams $e upstreamelectrcade. lmprogledegltaw conditions adjacent UNHE e upstream e ectroe are pro uc y provl mg a senes 0 2,297,818 10/1942 Van Sickle 200/148jets issuing from circumferentially-spaced points about the 2,494,661I/I950 Latour 200/148 orifice opening and directed convergently towardthe central 3,180,959 4/1965 MacNeill et a1. 200/148 region of thedownstream face of the upstream electrode.

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I N4 l 1 x 12 Pate nted May-18,1971 3,579,258

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' ATTORNLY Pat nt Ma -18,1971 3 519,258

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mum/ran:

JOHN W. BL'ATTY,

- 8y ATTORNEY GAS BLAST CIRCUIT BREAKER USING .A GENERALLY FLOW MAINBLAST This invention relates to a gas blast circuit breaker of the typeusing a generally axial flow main blast and, more particularly, to meansfor improving the interrupting ability of such a circuit breaker.

The usual gas blast circuit breaker comprises means for establishing anelectric arc across a gap between two electrodes and means for directinga high velocity blast of gas into the arcing region. The purpose of thegas blast is to cool the arc and to scavenge the arcing region of arcingproducts so as to increase the rate at which dielectric strength isbuilt up across the gap when the current zero point is reached. Byincreasing this rate of dielectric recovery, it is possible to improvethe ability of the gap to withstand the usualrecovery voltage transientwhich builds up as soon as current zero is reached, thus improving theinterrupting ability of the circuit breaker.

In an axial blast type of circuit greater, there is typically providedan orifice through which the are between the electrode extends andthrough which the gas blast flows axially of the arc about-the peripheryof the arc. The purpose of the orifice is to guide the blast withrespect to the arc and to impart the desired high velocity to the blast.The electrode that is located upstream from the orifice is referred tohereinafter as the upstream electrode, and the electrode that is locateddownstream from the orifice is referred to hereinafter as the downstreamelectrode.

In the typical axial blast circuit breaker, there is a stagnation zoneon the downstream side of the upstream electrode. The gas blast thatflows past the upstream electrode toward the orifice opening separatesfrom the surface of the upstream electrode adjacent its downstream sideand creates this stagnation zone radially inwardly of the region atwhich such separation occurs. Typically, the gas blast forces theupstream terminal of the arc into the stagnation zone and holdsitcaptive therein. From an interrupting ability viewpoint, this is not anideal position in which to maintain the upstream arc terminal Both thescavenging process and the arc cooling process are ordinarily relativelyinefi'tcient in the stagnation zone, because the gas in this zone tendsto move in large scale eddies of relatively low velocity; and this lowvelocity detracts from both scavenging and arc cooling.

An object of the present invention is to increase the efficiency of boththe scavenging and the arc-cooling processes in this zone at thedownstream side of the upstream electrode.

Another-object is to force the gas blast to adhere more closely to thedownstream side of the upstream electrode,

thereby improving the scavenging in this region, and to do this by meanswhich involves no modification of the simple upstream electrodetypically used in this type circuit breaker.

In carrying out my invention in one form, l.provide a gas blast circuitbreaker that comprises an upstream electrode, a downstream electrode,and an orifice having an opening positioned between said electrodes.During an interrupting operation, an arc is established between theelectrodes that extends through the orifice opening, and a blast of gasis caused to flow through the orifice opening via paths extending alongthe external surface of the upstream electrode and generally axially ofthe are adjacent said upstream electrode. The upstream electrode has adownstream surface facing the orifice opening, and the gas blast tendsto separate from this downstream surface as it travels toward theorifice opening, leaving a low velocity zone centrally of the downstreamsurface. For modifying the path of the blast, I produce a series of jetswhich issue from circumferentially spaced points around the orificeopening and are directed convergently toward the central region of saiddownstream surface. These jets coact with the gas blast to deflect ittoward the center of downstream surface, thus causing it to adhere moreclosely to the downstream surface, thereby reducing the size and effectof the stagnation zone.

For a better understanding of my invention, reference may be had to thefollowing description taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a cross-sectional view of a portion of a predominantly axialblast circuit breaker embodying one form of my invention.

FIG. 2 is a cross sectional view of certain parts of conven, tionalaxial blast circuit breaker.

FIG. 3 is a diagrammatic plan view of the circuit breaker of FIG. 1 withportions broken away to show internal features.

Referring now to FIG. I, the circuit interrupter shown therein is of thesustained-pressure, gas-blast type described and claimed in my US. Pat.2,783,338, assigned to the assignee of the present invention. Only thoseparts of the interrupter that are considered necessary to provide anunderstanding of the present invention have been shown in FIG. I. In.this respect, only the right-hand portion of the interrupter as beenshown in section inasmuch as the interrupter is generally symmetricalwith respect to a vertical plane and the left-hand portion issubstantially identical to the right-hand portion. As described indetail in my above-mentioned patent, the interrupter comprises a casing12 which is normally filled with pressurized gas to define aninterrupting chamber 11. Located within the interrupting chamber 11 area pair of relatively movable contacts 14 and 16 which can be separatedto draw an arc within the pressurized gas within the chamber 11. Thecontact 14 is relatively stationary, whereas the other contact 16 ismounted for pivotal motion about a fixed, currentcarrying pivot 18. Whenthe movable contact 16 is driven clockwise about the pivot 18 from itssolid-line closed position of FIG. 1, an arc is established in theregion where the contacts part. The movable contact 16 is shown bydotted lines in FIG. 1 in a partially open position through which itpasses during a circuit-interrupting operation after having establishedan arc.

The movable contact 16 is supported by means of its current-carryingpivot 18 on a conductive bracket 19 that is preferably fonned integralwith a stationary cylinder 32. The cylinder 32 at its lower end issuitably supported from a generally cylindrical casting 33. The casting33 at its lower end is suitably secured to a flange 35 rigidly carriedby the stationary metallic casing 12.

For producing a gas blast to aid in extinguishing the arc, thecylindrical casting 33 contains a normally closed exhaust passage 36leading from the interrupting chamber 11 to the surrounding atmosphere.The casting 33 at its upper end is provided with a tubular nozzle member38 having an orifice portion 39 at its outer'end defining an inlet 37 tothe exhaust passage 36. This inlet 37 is referred to hereinafter as theorifice opening. The flow of arc-extinguishing gas through the tubularnoule 38 and the exhaust passage 36 is controlled by means of acylindrically shaped reciprocable blast valve member 40 located at theouter, or lower, end of the exhaust passage 36. This blast valve member40 normally occupies a solid-line, closed position wherein an annularflange 42 formed at its lower end sealingly abuts against a stationaryvalve seat 34 carried by the exhaust casting 33.

During a circuit interrupting operation, the movable blast valve member40 is driven upwardly from its solid-line, closed position of FIG. 1through a partially open intermediate position shown in dotted lines inFIG. 1. Opening of the valve member 40 allows pressurized gas in thechamber 11 to flow at high speed through the orifice opening 37 andnozzle 38 and out the exhaust passageway 36'past the valve member 40 toatmosphere as indicated by the dotted line arrows B of FIG. 1. Themanner in which the gas blast acts to extinguish the arc will soon bedescribed in greater detail.

At its upper end, the cylindrical blast valve member 40 surrounds aprojecting tubular support 41 upon which the valve member 40 is smoothlyslidable. The tubular support 41 is fixed to the casting 33 by suitablemeans (not shown). A compression spring 44 positioned between themovable valve member 40 and the lower end of support 41 tends to holdthe valve member 40 in its closed position against the valve seat 0protect the support 41 and the upper end of the valve member 40 from theharmful effects of arcing, a protective I metallic tube 43 is positionedabout these parts and is suitably secured to the support- 41. Adjacentthe outer surface of this tube is a downstream probe or electrode'45,preferably of a refractory metal, which is located in the path of the,gas blast flowing through the passageway 36. This electrode 45 issupported on and electrically connected to casting 33 by a conductiverod 45a. As will soon appear more clearly, the downstream terminal ofthe arc is transferred to this electrode 45 during an interruptingoperation and, after such transfer, occupies a position generallycorresponding to that shown at- 46. The downstream terminal of an arereaching the electrode 45 attaches to the electrode and is thusprevented from being driven further downstream by the gas blast.

For controlling the operation .of the movable blast valve Y40 andmovable contact 16, a combined operating mechanism 50 is provided. Thismechanism 50 is preferably constructed in the manner disclosed andclaimed in my aforementioned US. Pat. No. 2,783,338, and its detailsform no part of the present invention. Generally speaking, thismechanism 50 comprises a blast valve-controlling piston i and acontact-controlling piston 52 mounted within thecylinder-32. The blastvalvecontrolling piston 51 is coupled to the movable blast valvemember40 through a piston rod 54 suitably clamped to the valve member40. The contact-controlling piston 52, on the other hand, is connectedto the movable contact 16 through a piston rod 58 and a cross head 59secured to the piston rod. A link 60 pivotally joined to the cross head59 and 61 and to the movable contact 16 at 62 interconnects the crosshead 59 and the movable contact 16. When the blast valve-controllingpiston 51 is driven upwardly, it acts to open the blast valve member 40,and, simultaneously, to drive the contact-con trolling piston 52-upwardly to produce opening movement of the movable contact member 16.

Opening movement of the contact member 16 first establishes an arebetween the ends of the contacts 14 and 16. Shortly thereafter, however,the blast of gas which has been flowing through the orifice opening 37,as indicated by the dotted line arrows B, forces the upstream terminalof the are on to an upstream arcing electrode 70, which is electricallyconnected to the stationary contact l4 through a conductive support 71.As opening motion of the movable contact 16 continues, the gas blastforces the downstream terminal of the arc to transfer from the movablecontact 16 to orifice struc ture 39, which is electrically connected tothe movable contact 16. The gas'blast then impels the downstreamterminal of the arc through the orifice opening 37 and nozzle 38 on tothe upper end of the protective metallic tube 43. From there, the gasblast drives the downstream arc terminal downwardly and onto theelectrode 45. The are then occupies the position generally shown in 46.When the arc is in this position, the arc column extends through theorifice opening 37 and is sub- I breaker to prevent the are fromreigniting at a current zero depends upon the rate at which dielectricstrength is recovered across the arcing region when arcing ceases atcurrent zero. The faster the'dielectric recovery rate, the lower thechances I for reignition and thus the better the chances for successfulinterruption at this time.

Substantial improvements in the dielectric recovery rate can be madelay-eliminating, or at least reducing the size 'of, the stagnation zonethat has existed at the downstream face of the upstream electrode 70 sothat this zone is for the most part, characterized by high velocitiesinstead of the low velocities previously present. The high velocitiespromote rapid cooling of the arc plasma and more efficient scavenging,thus improving the dielectric recove y rate.

The stagnation zone referred to in the immediately preceding paragraphis illustrated in FIG. 2, which shows a conventional upstream electrodeE being enveloped by an axial blast streams past the upstream electrodeE are designated B. As shown in FIG. 2, these paths B follow theexternal contour of the electrode E rather closely about the outerperiphery of the electrode but eventually separate from the surface ofthe electrode at points designated S in FlG.'2 near the outer peripheryof the downstream face of the electrode E. Radially inwardly of thesepoints S there is a zone 74 in which the gas flows at relatively lowvelocities in large scale eddies such as depicted at 75. This zone 74 isreferred to herein as the stagnation zone.

The upstream tenninal of an are established between the contacts 16 and14 is transferred from the contact 14 onto the upstream electrode 70 bythe gas blast following the paths B. The gas blast then drives theupstream terminal in the direction of the gas blast into the stagnationzone 74. As pointed out hereinabove, this is not an ideal position for'the arc terminal since the gas in this zone is flowing in large scaleeddies 75 at relatively low velocities, and these low velocities detractfrom both scavenging and are cooling.

In one typical circuit breaker, a passageway 77 extending through theupstream electrode 70 is provided primarily to deny the arc terminal apossibly stable footing at the center of the upstream electrode; Thereis some gas flow through this passage 77, but this gas flow is minor anddoesnot affect the basic flow pattern heretofore described as beingpresent in the stagnation zone. I

In accordance with the present invention, 1 very substantially reducethe size of the stagnation zone by producing a series of jets 80 whichissue from the orifice 39 at circumferentially spaced points around theorifice opening 37. As will be apparent from FlG.- 1, these jets 80 aredirected generally upstream with respect to the main gas blast andconvergently toward the central region of the downstream face of theupstream electrode. Their effect is to deflect the main gas blast'towardthe center of the downstream surface, thus causing the blast to adheremore closely to the downstream surface. Separation of the blast from thedownstream surface is prevented until the blast almost reaches thecentral passage 77. By sweeping'substantiall y the entire downstreamsurface with the high velocity main blast in this manner, Isubstantially improve the scavenging of arcing products in this regionand improve the dielectric recovery rate. These improvements areespecially notable in the switching of capacitance currents, a type ofduty which imposes particularly severe voltage conditions followingcurrent zero. a

For providing the jets 80, 1 form the orifice 39 with an annular headerpassage 82 that extends within the orifice wall completely around theorifice opening. Jet passages 84 communicate with this header passage 82at circumferentially spaced points along its length. Although FIG. 1shows only two of these jet passages 84, it is to be understood thatmany more are actually present at circumferentially spaced points 1around the orifice opening. The header passage 82 is connected to asource of pressurized gas at a pressure substantially higher than thepressure in the casing 12. This is schematically illustrated in FIG. 3,which shows an auxiliary tank 85 containing gas at a higher pressurethan the pressure in tank 12 connected through supply lines 86 and 87 toheader passages in the two orifices 39 of the circuit breaker. Anormally closed control valve 90 in line 86 normally prevents the highpressure gas from flowing into the main interrupting chamber 11. Thisvalve 90 is opened (by suitable means not shown) at an early stage in acircuit breaker-opening operation, whereupon high pressure gas fromauxiliary source 85 flows through lines 86 and 87 into the headerpassages 82 in the orifice 39, thus creating the previously describedjets issuing through the jet passages 84.

In the type of circuit breaker illustrated, it is customary to provide aresistor shunting each set of main contacts l6, 14 of the breaker. Thisresistor remains connected across the contacts during the circuitinterrupting operation for the purpose of reducing the rate of rise ofthe recovery voltage at current zero. The resulting current through theresistor is interrupted of gas. The primary flow paths followed by thegas blast as it 75 shortly thereafter by opening a resistor switchconnected in series with the resistor. A trated at and the resistor arenot shown since these can be conventional, as is shown for example inUS. Pat. No. 3,133,176 to Schneider, assigned to thesassignee of thepresent invention.

The illustrated resistor, switch comprises an orifice 102 through whichan auxiliary blast 103 flows when the blast valve 42 is opened. When theresistor switch is opened as above described, a relatively low currentare is established and immediately transferred to a position between anelectrode 105 inside the orifice 102 and an upstream electrode 106spaced from the orifice and supported on an insulator 108. This are iscooled by the auxiliary blast 103 in substantially the same manner asdescribed withrespect to the main orifice. Once again, however, there isthe problem of a stagnation zone developing in front of the downstreamface 107 of the upstream electrode 106 and detracting from the coolingand scavenging. To reduce the size and effect of the stagnation zone, Iprovide orifice 102 with substantially the same jetfomiing means themain orifice 39 is provided with. Accordingly, in orifice 102 there isan annular header passage 110 with jet passages 112 leading offtherefrom at circumferentially spaced points about the orifice opening.These jet passages, like jetv passages 84, are directed convergentlytoward the central region of the upstream electrode and serve to deflectthe blast toward the center of the downstream face 107, preventingseparation of theblast from the downstream face until the blast hasalmost reached the center of the downstream face.

Although the current interrupted at the resistor switch is relativelylow compared to that interrupted at the main con-. tacts, severe voltageconditions can develop at the resistor switch particularly duringcapacitance switching operations.

To enable the resistor switch to consistently withstand these voltageswithout-breakdown, it is important that the gap between the electrodesbe scavenged of dielectrically weak arcing products as soon as possible.The improved flow pattern resulting from the jets improves thisscavenging and thus improves the ability of the resistor switch towithstand the severe voltages accompanying capacitance-switchingoperations.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from myinvention in its broader aspects; and I, therefore, intend in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of my invention.

lclaim: I

l. A gas blast circuit breaker comprising a chamber containing gas at afirst pressure and further comprising:

a. an upstream electrode and a downstream electrode 7 located withinsaid chamber,

b. an orifice having an'opening positioned between said electrodes, c.means for establishing an are between said electrodes that extendsthrough said orifice opening,

d. means operative when said arc is established for causing a gas blastto flow through said orifice opening via paths that extend along theexternal surface of said upstream electrode and generally axially ofsaid arc adjacent said upstream electrode,

e. said upstream electrode having a downstream surface constituting aportion'of saidexternal surface and facing said orifice opening when anarc is present between said electrodes, and means for producing a seriesof gas jets issuing from said orifice at circumferentially spaced pointsabout said orifice opening and directed generally upstream with respectto said gas blast and convergently toward the central region of thedownstream face of the upstream electrode, thereby forcing said gasblast to adhere more closely to the downstream face of said upstreamelectrode.

2. The circuit breaker of claim 1 in combination with:

a. circumferentially spaced passageways for said jets extending throughsaid orifice, and

b. a reservoir for supplying gas to said jet passageways, said reservoircontaining gas at a higher pressure than said first pressure.

3. The circuit breaker of claim 1 in combination with:

' a. circumferentially spaced passageways for said jets extendingthrough said orifice,

b. a header passage located withing said orifice and extending aroundsaid orifice opening, and

c. means for supplying pressurized gas to said header passage to providehigh pressure gas for said jets.

4. The circuit breaker of claim 1 in combination with a resistor switchwithin said chamber for interrupting resistor current followingextinction of saidarc, said resistor switch comprising:-

a. an upstream electrode and a downstream electrode located within saidchamber,

b. an orifice having an opening positioned between said latterelectrodes,

0. means for establishing a resistor-switch are between saidresistor-switch electrodes that extends through said latter orificeopening,

d. means operative when 'said resistor-switch arc is established forcausing a blast of gas to fiow through said latter orifice opening viapaths that extend along the external surface of said resistor-switchupstream electrode and generally axially of said resistor-switch arcadjacent said upstream electrode,

.'sai d latter upstream electrode having a downstream surfaceconstituting a portion of said external surface and facing said latterorifice opening when the resistor switch arc is present between said.electrodes,

f. and means for producing a series of gas jets issuing from saidorifice of said resistor switch at circumferentially spaced points aboutsaid orifice opening of said resistor switch and directed generallyupstream with respect to said resistor switch gas blast and convergentlytoward the central region of the downstream face of the upstreamelectrode of said resistor switch.

5. The circuit breaker of claim 4 in which:

a. circumferentially spaced passageways for said jets extend throughboth of said orifices,

b. connecting means is provided for interconnecting all of said jetpassageways,

c. a reservoir is provided for supplying high pressure gas to all ofsaid jet passageways through said connecting means, said reservoircontaining gas at a higher pressure than said first pressure.

1. A gas blast circuit breaker comprising a chamber containing gas at afirst pressure and further comprising: a. an upstream electrode and adownstream electrode located within said chamber, b. an orifice havingan opening positioned between said electrodes, c. means for establishingan arc between said electrodes that extends through said orificeopening, d. means operative when said arc is established for causing agas blast to flow through said orifice opening via paths that extendalong the external surface of said upstream electrode and generallyaxially of said arc adjacent said upstream electrode, e. said upstreamelectrode having a downstream surface constituting a portion of saidexternal surface and facing said orifice opening when an arc is presentbetween said electrodes, f. and means for producing a series of gas jetsissuing from said orifice at circumferentially spaced points about saidorifice opening and directed generally upstream with respect to said gasblast and convergently toward the central region of the downstream faceof the upstream electrode, thereby forcing said gas blast to adhere moreclosely to the downstream face of said upstream electrode.
 2. Thecircuit breaker of claim 1 in combination with: a. circumferentiallyspaced passageways for said jets extending through said orifice, and b.a reservoir for supplying gas to said jet passageways, said reservoircontaining gas at a higher pressure than said first pressure.
 3. Thecircuit breaker of claim 1 in combination with: a. circumferentiallyspaced passageways for said jets extending through said orifice, b. aheader passage located withing said orifice and extending around saidorifice opening, and c. means for supplying pressurized gas to saidheader passage to provide high pressure gas for said jets.
 4. Thecircuit breaker of claim 1 in combination with a resistor switch withinsaid chamber for interrupting resistor current following extinction ofsaid arc, said resistor switch comprising: a. an upstream electrode anda downstream electrode located within said chamber, b. an orifice havingan opening positioned between said latter electrodes, c. means forestablishing a resistor-switch arc between said resistor-switchelectrodes that extends through said latter orifice opening, d. meansoperative when said resistor-switch arc is established for causing ablast of gas to flow through said latter orifice opening via paths tHatextend along the external surface of said resistor-switch upstreamelectrode and generally axially of said resistor-switch arc adjacentsaid upstream electrode, e. said latter upstream electrode having adownstream surface constituting a portion of said external surface andfacing said latter orifice opening when the resistor switch arc ispresent between said electrodes, f. and means for producing a series ofgas jets issuing from said orifice of said resistor switch atcircumferentially spaced points about said orifice opening of saidresistor switch and directed generally upstream with respect to saidresistor switch gas blast and convergently toward the central region ofthe downstream face of the upstream electrode of said resistor switch.5. The circuit breaker of claim 4 in which: a. circumferentially spacedpassageways for said jets extend through both of said orifices, b.connecting means is provided for interconnecting all of said jetpassageways, c. a reservoir is provided for supplying high pressure gasto all of said jet passageways through said connecting means, saidreservoir containing gas at a higher pressure than said first pressure.